Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2011	Jan. 31, 2011	Oct. 31, 2010
Derivative [Line Items]
Other assets and deferred charges	$ 4,967	$ 4,129	$ 4,194
Long-term debt due within one year	1,470	4,655	5,196
Long-term debt	44,872	40,692	40,803
Deferred income taxes and other	8,085	6,682	6,197
Fair Value Instruments [Member]
Derivative [Line Items]
Prepaid expenses and other	3
Other assets and deferred charges	210	267
Asset subtotals	213	267
Long-term debt due within one year	3
Long-term debt	210	267
Liability subtotals	213	267
Net Investment Instruments [Member]
Derivative [Line Items]
Other assets and deferred charges	291	233
Asset subtotals	291	233
Cash Flow Instruments [Member]
Derivative [Line Items]
Other assets and deferred charges	105	238
Asset subtotals	105	238
Deferred income taxes and other	81	18
Liability subtotals	$ 81	$ 18